U.S. patent application number 14/843208 was filed with the patent office on 2016-03-17 for inkjet nozzle device with roof actuator connected to lateral drive circuitry.
The applicant listed for this patent is Memjet Technology Limited. Invention is credited to Misty Bagnat, Brian Kevin Donohoe, Emma Rose Kerr, Vincent Patrick Lawlor, Gregory John McAvoy, Ronan Padraig Sean O'Reilly, Eimear Ryan.
Application Number | 20160075135 14/843208 |
Document ID | / |
Family ID | 54072868 |
Filed Date | 2016-03-17 |
United States Patent
Application |
20160075135 |
Kind Code |
A1 |
O'Reilly; Ronan Padraig Sean ;
et al. |
March 17, 2016 |
INKJET nozzle device with roof actuator connected to lateral drive
circuitry
Abstract
An inkjet printhead integrated circuit includes: a substrate
having a silicon layer; a nozzle plate disposed on the silicon
layer; and embedded inkjet nozzle devices. Each inkjet nozzle
device includes a nozzle chamber having a roof actuator; drive
circuitry laterally disposed relative to the nozzle chamber; a
connection arm extending parallel with the nozzle plate from the
actuator towards the drive circuitry; and a metal via
interconnecting each connection arm and the drive circuitry, the
metal via extending perpendicularly to the nozzle plate. The drive
circuitry is positioned proximal the nozzle plate relative to a
plane of the floor.
Inventors: |
O'Reilly; Ronan Padraig Sean;
(Dublin, IE) ; McAvoy; Gregory John; (Dublin,
IE) ; Kerr; Emma Rose; (Dublin, IE) ; Lawlor;
Vincent Patrick; (Dublin, IE) ; Bagnat; Misty;
(Dublin, IE) ; Donohoe; Brian Kevin; (Dublin,
IE) ; Ryan; Eimear; (Dublin, IE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Memjet Technology Limited |
Dublin 2 |
|
IE |
|
|
Family ID: |
54072868 |
Appl. No.: |
14/843208 |
Filed: |
September 2, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62051625 |
Sep 17, 2014 |
|
|
|
Current U.S.
Class: |
347/47 |
Current CPC
Class: |
B41J 2/14427 20130101;
B41J 2/1642 20130101; B41J 2/1433 20130101; B41J 2/1601 20130101;
B41J 2/1648 20130101; B41J 2/1628 20130101; B41J 2/14016 20130101;
B41J 2/1607 20130101; B41J 2002/1437 20130101; B41J 2202/18
20130101; B41J 2/14201 20130101; B41J 2202/13 20130101; B41J
2002/14435 20130101 |
International
Class: |
B41J 2/14 20060101
B41J002/14 |
Claims
1. An inkjet printhead integrated circuit comprising: a substrate
having at least one silicon layer; a nozzle plate disposed on the
silicon layer; and one or more embedded inkjet nozzle devices, each
inkjet nozzle device comprising: a nozzle chamber defined in the
silicon layer, each nozzle chamber comprising a floor having a
chamber inlet defined therein; a roof comprising an actuator and
part of the nozzle plate, the actuator being configured for
ejecting ink through a nozzle opening defined in the roof; and
silicon sidewalls extending from the floor to the roof; drive
circuitry laterally disposed relative to the nozzle chamber; one or
more connection arms extending parallel with the nozzle plate, each
connection arm extending from the actuator towards the drive
circuitry; and at least one metal via interconnecting each
connection arm and the drive circuitry, each metal via extending
perpendicularly to the nozzle plate, wherein the drive circuitry is
positioned proximal the nozzle plate relative to a plane of the
floor.
2. The inkjet printhead integrated circuit of claim 1, wherein a
height of the metal vias is less than a height of the nozzle
chamber.
3. The inkjet printhead integrated circuit of claim 1, wherein the
actuator and connections arms are coplanar.
4. The inkjet printhead integrated circuit of claim 3, wherein the
actuator and connections arms are comprised of a same material.
5. The inkjet printhead integrated circuit of claim 1, wherein the
actuator is selected from the group consisting of: a resistive
heating element, a thermoelastic material and piezoelectric
transducer.
6. The inkjet printhead integrated circuit of claim 1, wherein the
substrate is a silicon-on-insulator substrate having a first layer
of silicon, an insulator layer disposed on the first layer of
silicon and a second layer of silicon disposed on the insulator
layer, and wherein the nozzle chamber is defined in the second
layer of silicon.
7. The inkjet printhead integrated circuit of claim 6, wherein the
floor of each nozzle chamber comprises part of the insulator
layer.
8. The inkjet printhead integrated circuit of claim 6, wherein the
first layer of silicon is relatively thicker than the second layer
of silicon.
9. The inkjet printhead integrated circuit of claim 6, wherein a
height of each nozzle chamber corresponds to a thickness of the
second layer of silicon.
10. The inkjet printhead integrated circuit of claim 6, wherein at
least one ink channel is defined in the first layer of silicon.
11. The inkjet printhead integrated circuit of claim 1, wherein the
inkjet nozzle devices are arranged in rows, and wherein one or more
rows of the inkjet nozzle devices receive ink from a common ink
feed channel via respective chamber inlets.
12. The inkjet printhead integrated circuit of claim 1, wherein the
nozzle plate comprises a plurality of layers.
Description
FIELD OF THE INVENTION
[0001] This invention relates to printhead integrated circuits
comprising inkjet nozzle devices. It has been developed primarily
for producing robust, low-cost printheads having efficient current
transfer from drive circuitry to MEMS actuators
BACKGROUND OF THE INVENTION
[0002] The Applicant has developed a range of Memjet.RTM. inkjet
printers as described in, for example, WO2011/143700, WO2011/143699
and WO2009/089567, the contents of which are herein incorporated by
reference. Memjet.RTM. printers employ a stationary pagewidth
printhead in combination with a feed mechanism which feeds print
media past the printhead in a single pass. Memjet.RTM. printers
therefore provide much higher printing speeds than conventional
scanning inkjet printers.
[0003] An inkjet printhead is comprised of a plurality (typically
thousands) of individual inkjet nozzle devices, each supplied with
ink. Each inkjet nozzle device typically comprises a nozzle chamber
having a nozzle aperture and an actuator for ejecting ink through
the nozzle aperture. The design space for inkjet nozzle devices is
vast and a plethora of different nozzle devices have been described
in the patent literature, including different types of actuators
and different device configurations.
[0004] Most current inkjet printheads comprise one or more MEMS
printhead integrated circuits, whereby inkjet nozzle devices are
fabricated on a CMOS silicon wafer using MEMS fabrication
techniques. Integration of MEMS and CMOS features is a crucial
aspect of MEMS printhead design.
[0005] Research Disclosure 596074 and U.S. Pat. No. 6,938,340
describe inkjet nozzle devices comprising a MEMS layer disposed on
a silicon-on-insulator substrate. The insulator layer facilitates
control of backside ink channel etch processes.
[0006] Some types of inkjet nozzle devices employ an actuator
bonded to the roof of a nozzle chamber. For example, U.S. Pat. No.
7,654,645 describes thermal bubble-forming actuators bonded to the
roof of the nozzle chamber; U.S. Pat. No. 5,812,162 describes
thermal actuators bonded to the roof of the nozzle chamber, which
warm ink to reduce surface tension and cause droplet ejection; U.S.
Pat. No. 7,819,503 describes nozzle chambers having a moving roof
portion comprising a thermoelastic bend actuator; and U.S. Pat. No.
5,828,394 describes a nozzle chamber having a moving roof portion
comprising piezoelectric actuator.
[0007] Roof-bonded actuators present different design challenges
compared to more usual floor-bonded actuators. This is because
MEMS-CMOS integration must deliver power efficiently from drive
transistors in the CMOS layer up to the actuators in the MEMS
layer, inevitably using electrical connectors which extend over a
height of the nozzle chamber. This, in turn, places practical
limitations on nozzle chamber heights.
[0008] U.S. Pat. No. 7,794,056 and U.S. Pat. No. 7,819,503 describe
two different types of electrical connectors for delivering current
to a thermoelastic actuator positioned in a moving portion of a
nozzle chamber roof.
[0009] It would be desirable to provide a printhead have excellent
nozzle plate robustness. It would further be desirable to provide
an improved fabrication process for integrating MEMS and CMOS
features. It would further be desirable to provide inkjet nozzle
devices having roof actuators with excellent electrical efficiency
and, particularly, power transfer from drive circuitry which is
independent of nozzle chamber height.
SUMMARY OF THE INVENTION
[0010] In accordance with a first aspect of the present invention,
there is provided an inkjet printhead integrated circuit
comprising:
a silicon-on-insulator substrate having a first layer of silicon,
an insulator layer disposed on the first layer of silicon and a
second layer of silicon disposed on the insulator layer; a nozzle
plate disposed on the second layer of silicon; and one or more
embedded inkjet nozzle devices, each inkjet nozzle device
comprising:
[0011] a nozzle chamber defined in the second layer of silicon,
each nozzle chamber comprising: a roof defining a respective nozzle
opening, the roof comprising part of the nozzle plate; a floor
comprising part of the insulator layer; and sidewalls extending
from the floor to the roof, the second layer of silicon defining
the sidewalls;
[0012] an actuator for ejecting ink through the nozzle opening;
and
[0013] drive circuitry connected to the actuator.
[0014] Printhead integrated circuits ("printhead chips") according
to the first aspect advantageously make use of silicon-on-insulator
(SOI) wafers so as to provide novel, embedded inkjet nozzle
devices. Conventional MEMS fabrication processes build up MEMS
structures on a passivated CMOS layer. In the conventional process,
MEMS structures are built up by a series of deposition, masking and
etching steps, with the height of ink chambers being defined by the
height of one of the deposited layers. For example, in some
commercial printers, ink chambers are defined in a deposited
polymeric layer (e.g. SU8); in other commercial printers, ink
chambers are constructed from a deposited ceramic material (e.g.
silicon nitride or silicon oxide). Inevitably, the conventional
MEMS fabrication techniques introduce potential problems such as
planarity, robustness, limitations on nozzle chamber heights, power
transfer from drive circuitry etc.
[0015] By contrast, the printhead integrated circuits according to
the first aspect ameliorate at least some of these problems and
offer a novel approach to MEMS printhead design and fabrication.
With a nozzle plate deposited directly on an SOI wafer, potential
problems of nozzle plate planarity are, to a large extent, avoided.
With a planar nozzle plate and inkjet devices embedded in the
subjacent silicon layer, the printheads have greater mechanical
robustness than conventional MEMS printheads. With the nozzle
chamber defined in a frontside silicon layer of an SOI wafer, there
are fewer limitations on the maximum chamber height achievable from
conventional MEMS deposition processes. Furthermore, electrical
connections to CMOS drive circuitry, typically laterally disposed
relative to each nozzle chamber, are simplified. These and other
advantages of the present invention will be readily apparent from
the detailed description hereinbelow.
[0016] Preferably, the first layer of silicon is relatively thicker
than the second layer of silicon. The second layer of silicon may
have a thickness in the range of 5 to 50 microns, while the first
layer of silicon is bulk silicon which may have a thickness in the
range of 100 to 1000 microns. The separating insulator layer is
typically comprised of silicon dioxide, as known in the art, and
has a thickness in the range of 1 to 10 microns. CMOS circuitry is
integrated into the second layer during SOI wafer production.
[0017] Preferably, a height of each nozzle chamber corresponds to a
thickness of the second layer of silicon. The nozzle chamber is
generally defined by etching the second layer down to the insulator
layer, which acts as an etch stop for a frontside chamber etch.
[0018] Preferably, a chamber inlet is defined in the floor of each
nozzle chamber. The chamber inlet may be defined by a frontside or
backside etch of the insulator layer, depending on the particular
sequence of MEMS fabrication steps employed.
[0019] Preferably, the roof comprises the actuator. The roof
actuator may be, for example, a thermal bubble-forming resistive
heater element (see, for example, U.S. Pat. No. 7,654,645); a
surface tension-reducing heater element (see, for example U.S. Pat.
No. 5,812,162); a thermoelastic bend actuator (see, for example,
U.S. Pat. No. 7,819,503) or a piezoelectric transducer (see, for
example, U.S. Pat. No. 5,828,394).
[0020] Depending on the type of actuator employed, it may be bonded
to a lower surface or an upper surface of the roof, or sandwiched
between different layers within the roof. For example, a thermal
bend actuator may comprising a thermoelastic element bonded to an
upper surface of a passive element so as to provide a moving roof
portion, which bends towards the floor of the nozzle chamber upon
actuation. On the other hand, a resistive heater element may be
bonded to a lower surface of the roof so as to maximize thermal
contact with ink inside the nozzle chamber.
[0021] The roof comprises part of the nozzle plate, which may be
comprised of one or more different layers. For example, the nozzle
plate may comprise a monolayer of silicon oxide or a monolayer of
silicon nitride. Alternatively, the nozzle plate may be bi-layered
comprising a layer of silicon oxide and a layer of silicon nitride.
Further nozzle plate layers are also within the ambit of the
present invention. In some embodiments, the nozzle plate may
comprise a coating, for example, to facilitate efficient printhead
maintenance or cover any exposed actuators to prevent electrical
shorting via ink across the nozzle plate. The coating may comprise,
for example, a polymer coating, such as polydimethylsilicone
(PDMS), a polysilsesquioxane (PSQ), an epoxy-based photoresist
(e.g. SU-8) etc. Alternatively, the coating may comprise a low-k
dielectric material.
[0022] Preferably, the drive circuitry is laterally disposed
relative to the nozzle chamber; that is, at one side of one of the
sidewalls. The drive circuitry is typically CMOS circuitry
comprising a plurality of metal layers (e.g. 2 to 4 layers)
separated from each by interlayer dielectric (ILD) layers.
[0023] Preferably, the drive circuitry is positioned proximal the
nozzle plate relative to the insulator layer of the SOI substrate
and/or a plane containing the floor of the nozzle chamber. This
arrangement contrasts with conventional inkjet nozzle devices,
where the drive circuitry is usually positioned distal from the
nozzle plate relative to a plane containing the floor of the nozzle
chamber.
[0024] Preferably, each inkjet nozzle device further comprises one
or more connection arms extending parallel with the nozzle plate,
each connection arm extending from the actuator towards the drive
circuitry. Preferably, the actuator and connections arms are
coplanar and comprised of a same material by virtue of a
co-deposition process.
[0025] Preferably, each inkjet nozzle device further comprises at
least one metal via interconnecting each connection arm and the
drive circuitry, each metal via extending perpendicularly to the
nozzle plate. The metal via is typically comprised of copper and
may be formed using a damascene-like process. Preferably, a height
of the metal vias is less than a height of the nozzle chamber.
Since the lengths of the electrical connections to drive circuitry
is independent of the height of the nozzle chamber, excellent
electrical efficiency and power transfer can be achieved by
minimizing the length of the current path.
[0026] Preferably, at least one ink feed channel is defined in the
first layer of silicon. Preferably, the inkjet nozzle devices are
arranged in rows, wherein one or more rows of the inkjet nozzle
devices receive ink from a common ink feed channel via respective
chamber inlets. For example, one common ink feed channel may supply
ink to a pair of nozzle rows in a multi-color printhead.
Alternatively, one common ink feed channel may supply ink to
multiple nozzle rows in a monochrome printhead.
[0027] In accordance with a second aspect, there is provided an
inkjet printhead integrated circuit comprising:
a substrate having at least one silicon layer; a nozzle plate
disposed on the silicon layer; and one or more embedded inkjet
nozzle devices, each inkjet nozzle device comprising:
[0028] a nozzle chamber defined in the silicon layer, each nozzle
chamber comprising a floor having a chamber inlet defined therein;
a roof comprising an actuator and part of the nozzle plate, the
actuator being configured for ejecting ink through a nozzle opening
defined in the roof; and silicon sidewalls extending from the floor
to the roof;
[0029] drive circuitry laterally disposed relative to the nozzle
chamber;
[0030] one or more connection arms extending parallel with the
nozzle plate, each connection arm extending from the actuator
towards the drive circuitry; and
[0031] at least one metal via interconnecting each connection arm
and the drive circuitry, each metal via extending perpendicularly
to the nozzle plate, wherein the drive circuitry is positioned
proximal the nozzle plate relative to a plane of the floor.
[0032] It will be appreciated that preferred embodiments of the
first aspect are applicable mutatis mutandis to the second
aspect.
[0033] Likewise, the substrate employed in the second aspect may be
a silicon-on-insulator substrate having a first layer of silicon,
an insulator layer disposed on the first layer of silicon and a
second layer of silicon disposed on the insulator layer, wherein
the nozzle chamber is defined in the second layer of silicon. In
this preferred embodiment, the floor of each nozzle chamber
preferably comprises part of the insulator layer.
[0034] As used herein, the term "ink" refers to any ejectable fluid
and may include, for example, conventional CMYK inks, infrared
inks, UV-curable inks, fixatives, 3D printing materials, polymers,
biological fluids etc.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Embodiments of the present invention will now be described
by way of example only with reference to the accompanying drawings,
in which:
[0036] FIG. 1 is a cutaway perspective view of part of a printhead
integrated circuit comprising an inkjet nozzle device according to
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0037] Referring to FIG. 1, there is shown part of a printhead
integrated circuit 10 ("printhead IC") according to the present
invention comprising a plurality of inkjet nozzle devices 100
arranged in rows. Only one nozzle device 100 is shown in FIG. 1,
although it will be appreciated that the printhead IC 10 may
contain plurality of nozzle devices arranged in rows, as is well in
known in the art.
[0038] The printhead IC 10 is based on a silicon-on-insulator wafer
substrate comprising a first silicon layer 14, a second silicon
layer 16 and an insulator layer 18, typically silicon oxide,
sandwiched between the first and second silicon layers. As is
typical in SOI wafers, the first silicon layer 14 is relatively
much thicker than the second silicon layer 16. Typically, the
second silicon layer 16 has a thickness in the range of 5 to 50
microns, the thickness being defined by the SOI wafer fabrication
process. The first silicon layer 14 may have a thickness in the
range of 100 to 1000 microns, the thickness usually being
determined by an extent of backside grinding or etching as part of
the printhead IC MEMS fabrication process.
[0039] A nozzle plate 20 is disposed on the second silicon layer
16. The nozzle plate 20 may be mono-layered, but more usually
comprises a plurality of layers. As shown in FIG. 1, the nozzle
plate comprises a tetraorthosilicate layer 22 deposited by
plasma-enhanced chemical vapour deposition ("PETEOS layer"). The
PETEOS layer 22 serves primarily as a passivating dielectric layer
for insulating underlying CMOS drive circuitry 24. The nozzle plate
further comprises a silicon nitride layer 26 disposed on the PETEOS
layer 22, and a relatively thinner silicon oxide layer 28 disposed
on the silicon nitride layer. The silicon nitride and oxide layers
26 and 28 define a ceramic roof for each nozzle chamber 30 of the
inkjet nozzle device 100 as well defining a passive beam element
for a thermal bend actuator. The combination of silicon nitride and
silicon oxide layer advantageously minimizes cracking during
fabrication and operation, and additionally maximizes thermal
insulation of a thermoelastic beam element 32 disposed on the
silicon oxide layer. These advantages are described in more detail
in U.S. Pat. No. 8,079,668, the contents of which are herein
incorporated by reference.
[0040] In the embodiment shown in FIG. 1, the nozzle plate further
comprises an upper coating layer 34, which provides additional
robustness and electrically insulates actuators from any
adventitious conductive material (e.g. ink, fibres etc.) on the
nozzle plate which may bridge between adjacent actuators and
potentially cause shorting. The coating layer 34 may be comprised
of a material, which provides surface characteristics optimized for
printhead maintenance and fluidic management. Typically, a
relatively hydrophobic coating layer 34 is preferred, such as a
polymer, as described in U.S. Pat. No. 8,342,650, the contents of
which are incorporated herein by reference.
[0041] Still referring to FIG. 1, each inkjet nozzle device 100 is
embedded in the second silicon layer 16. The nozzle chamber 30 is
defined in the second silicon layer 16 and comprises: a floor 35
comprising part of the insulator layer 18; a roof comprising part
of the nozzle plate (layers 26, 28 and 34 as shown in FIG. 1); and
sidewalls 37 extending between the floor and the roof, the
sidewalls being silicon sidewalls defined by the second silicon
layer 16. A chamber inlet 39 is defined in the floor 35, and a
nozzle opening 41 is defined in the roof of the nozzle chamber 30.
The nozzle opening 41 is typically offset from the chamber inlet
39.
[0042] Since the nozzle chamber 30 is defined by etching the second
silicon layer 16, the height of the nozzle chamber generally
corresponds to the height of the second silicon layer. Accordingly,
relatively higher nozzle chambers may be provided by the present
invention, which may not be feasible using the conventional MEMS
deposition processes described in, for example, U.S. Pat. No.
7,819,503 and U.S. Pat. No. 6,755,509.
[0043] Suitable etch chemistries for selective frontside etching of
the nozzle chamber 30 and chamber inlet 39 will be readily apparent
to the person skilled in the art. The nozzle chamber 30 may be
defined by DRIE of the second silicon layer 16 using, for example,
a `Bosch` etch (see U.S. Pat. No. 5,501,893) or other suitable etch
chemistry (e.g. SF.sub.6/O.sub.2/Ar). The chamber inlet 39 may be
selectively etched using any suitable oxide etch chemistry (e.g.
C.sub.4F.sub.8/O.sub.2).
[0044] The roof of the nozzle chamber 30 comprises an actuator for
ejecting ink droplets through the nozzle opening 41 during use. In
the embodiment shown in FIG. 1, the actuator is a thermal bend
actuator comprising a thermoelastic beam element 32 and an
underlying passive beam element comprised of the dual silicon
nitride and silicon oxide layers 26 and 28. The roof comprises a
moving portion 43 comprising the thermal bend actuator and a
stationary portion 45. During actuation of the device, the
thermoelastic beam element 32 receives an electrical pulse from the
CMOS drive circuitry 24. The thermoelastic beam element 32 rapidly
heats and expands relative to the underlying passive beam element,
which causes bending of the moving portion 43 towards the floor 35
of the nozzle chamber 30, resulting in droplet ejection through the
nozzle opening 41.
[0045] Roof-actuated thermal bend actuator devices have been
described in detail in, for example, U.S. Pat. No. 7,794,056, the
contents of which are incorporated herein by reference. Suitable
materials for the thermoelastic beam element 32 include aluminium
alloys, such as titanium-aluminium and vanadium-aluminium.
[0046] Suitable fabrication methods for forming the nozzle plate,
including the roof of each nozzle chamber 30, are described in U.S.
Pat. No. 7,866,795, the contents of which are incorporated herein
by reference.
[0047] The CMOS drive circuitry 24, which provides current to the
thermoelastic beam element 32, is laterally disposed relative to
one sidewall 37 of the nozzle chamber 30. As shown in FIG. 1, the
CMOS drive circuitry 24 comprises four metal layers, although it
will be appreciated that any number of metal CMOS layers may be
employed. The CMOS drive circuitry 24 is proximal the nozzle plate
relative to the insulator layer 18 and the floor 35 of the nozzle
chamber 30. Thus, the overall design of the inkjet nozzle device
100 minimizes the length of the current path between the drive
circuitry 24 and the roof actuator, and makes the length of this
current path independent of the height of the nozzle chamber 30
containing the roof actuator.
[0048] The thermoelastic beam element 32 is connected to the CMOS
drive circuitry 24 via connection arms 46, each of which, in turn,
is connected to an uppermost metal CMOS layer (M4) through copper
vias 48. Each connection arm 46 (only one shown in FIG. 1) extends
parallel with the nozzle plate from the thermoelastic beam element
32 towards the CMOS drive circuitry 24. Each connection arm 46 is
coplanar and contiguous with the thermoelastic beam element 32,
being comprised of the same material and deposited in one layer
during MEMS fabrication. Suitable masking and etching of this layer
defines the thermoelastic beam element 32 and contiguous
connections arms 46 simultaneously in one fabrication step.
[0049] The copper vias 48 extend perpendicularly relative to the
nozzle plate down to the uppermost CMOS layer. The copper vias are
formed by first etching through the PETEOS layer 24, the silicon
nitride layer 26 and the silicon oxide layer 28 to form vias,
depositing a copper layer to fill the vias, and planarizing using,
for example, chemical-mechanical-planarization (CMP) stopping on
the silicon oxide layer 28. An analogous damascene-like process was
described in U.S. Pat. No. 8,453,329, the contents of which are
incorporated herein by reference.
[0050] The printhead IC 10 has at least one backside ink feed
channel 50 defined in the first silicon layer 14. By analogy with
the process described in Research Disclosure 596074, it will be
appreciated that the insulator layer 18 provides an etch-stop for
this backside etch.
[0051] In a monochrome printhead IC, all inkjet nozzle devices 100
may receive ink from a common backside ink feed channel 50 via
respective chamber inlets 39 defined in the insulator layer 18.
However, ink feed channel arrangements, such as those described in
U.S. Pat. No. 7,441,865 (the contents of which are incorporate
herein by reference) may, of course, be employed for multi-color
printheads. Typically, one ink feed channel supplies ink to a pair
of nozzle rows ("odd" and "even" nozzle rows) in a multi-color
printhead.
[0052] Multiple printhead ICs 10 may be combined to form an inkjet
printhead assembly, such as a pagewide inkjet printhead assembly.
The printhead ICs 10 may be butted end-on-end as described in, for
example, U.S. Pat. No. 7,441,865. Alternatively, the printhead ICs
10 may be combined in a staggered overlapping arrangement, as
described in, for example, U.S. Pat. No. 6,394,573; U.S. Pat. No.
6,409,323 and U.S. Pat. No. 8,662,636, the contents of each of
which are incorporated herein by reference. Accordingly, various
types of inkjet printers employing the printhead ICs 10 will be
readily apparent to the person skilled in the art.
[0053] It will, of course, be appreciated that the present
invention has been described by way of example only and that
modifications of detail may be made within the scope of the
invention, which is defined in the accompanying claims.
* * * * *